1. Cross-Reference to Related Application
This is a continuation of copending application Ser. No. 138,594, filed on Dec. 28, 1987, now abandoned, which is a continuation-in-part application of U.S. Pat. Application Serial No. 06/826,283 filed Feb. 5, 1986, now abandoned.
2. Field of the Invention
This invention relates to aircraft fuel tanks and, more particularly, to nestable aircraft external fuel tanks that may be quickly assembled and disassembled.
3. 3. Description of the Related Art
In conjunction with its military air operations, the United States Navy stores external aircraft fuel tanks aboard its aircraft carriers for extending the flight range of its carrier-based aircraft. The external fuel tanks used on carrier-based aircraft must be capable of withstanding a variety of loads. Carrier operations include rapid acceleration from a catapult launch that virtually throws an aircraft off the flight deck and includes the violent landing and sudden braking from an arresting cable. In addition, the tank is subjected to the usual flight loads and environmental conditions to which all external stores are exposed.
The number of external aircraft fuel tanks that can be stored on a carrier is limited because of the extreme bulkiness of the fuel tanks and the limited storage space aboard a carrier. As a result of this problem, the Navy has suggested disassembling aircraft fuel tanks into storable sections that can be assembled on board ship for combat-readiness support. See "Physical Distribution System for Aircraft External Fuel Tanks - Survey," Report No. CMLD-CR-47-85, SRI Final Report 8345, June 1985 (hereinafter the "SRI Report"). The basic functional requirements discussed in the SRI Report include the provision of a tank that can contain 200 to 400 gallons of fuel and that has attachment provisions for securely fastening the external fuel tank to an aircraft wing or fuselage. The fuel tank also must be capable of ejection, so that the pilot may jettison the fuel tank when empty or partially full. The tanks must also withstand the internal pressure due to the normal pressurization of fuel in the tank. Of course, the tank must endure the forces encountered from carrier catapult launches, arrested landings, and flight acceleration or "9" forces. The fuel tank also must include the usual fuel transfer mechanisms including fuel level and pressure transducers, plumbing, and valves for disconnecting the tank with the aircraft and for venting or dumping fuel. The tanks must be safe, in that they should radiate no toxic fumes, be rupture-proof, shatter-proof, and non-flammable, and be able to withstand high fuel afterburner temperatures. The fuel tank also must meet requirements for storage density and fuel tank assembly time, the goal for assembly time aboard ship being six minutes. Among others, the SRI Report lists objectives of minimum weight, minimum cost, durability, temperature resistance, and non-toxicity.
The SRI Report suggests many conventional concepts of joining the aircraft fuel tank sections upon assembly. These concepts include lap joints using adhesives; composite windings; circumferential clamps; mechanical fasteners such as bolts and rivets; robotic welding of metallic tank elements; explosive welding; and mounting plates. These conventional concepts of joining tank sections suffer from the disadvantage of requiring excessive time and manpower for assembly. Some of the concepts also involve hazardous methods or materials. In preparing the SRI Report, many persons who are skilled in the art were contacted, including most of the major United States defense aircraft manufacturers. Although the SRI Report discusses all manner of assembly configurations, it does not discuss the concept of the present invention. An object of the present invention is to provide an aircraft external tank comprising nestable sections that may be assembled and disassembled with minimum time and manpower.